/*
    Custom handlebars helpers which allows to make

    {{#is a '===' b}}}

    {{/is}}
*/

module.exports.register = function (handlebars) {

  var isArray = function(value) {
    return Object.prototype.toString.call(value) === '[object Array]';
  };

  var ExpressionRegistry = function() {
    this.expressions = [];
  };

  ExpressionRegistry.prototype.add = function (operator, method) {
    this.expressions[operator] = method;
  };

  ExpressionRegistry.prototype.call = function (operator, left, right) {
    if ( ! this.expressions.hasOwnProperty(operator)) {
      throw new Error('Unknown operator "'+operator+'"');
    }

    return this.expressions[operator](left, right);
  };

  var eR = new ExpressionRegistry;
  eR.add('not', function(left, right) {
    return left != right;
  });
  eR.add('>', function(left, right) {
    return left > right;
  });
  eR.add('<', function(left, right) {
    return left < right;
  });
  eR.add('>=', function(left, right) {
    return left >= right;
  });
  eR.add('<=', function(left, right) {
    return left <= right;
  });

  eR.add('==', function(left, right) {
    return left == right;
  });

  eR.add('===', function(left, right) {
    return left === right;
  });
  eR.add('!==', function(left, right) {
    return left !== right;
  });
  eR.add('in', function(left, right) {
    if ( ! isArray(right)) {
      right = right.split(',');
    }
    return right.indexOf(left) !== -1;
  });

  var isHelper = function() {
    var args = arguments
      ,   left = args[0]
      ,   operator = args[1]
      ,   right = args[2]
      ,   options = args[3]
        ;


        // console.log(args);

    if (args.length == 2) {
      options = args[1];
      if (left) return options.fn(this);
      return options.inverse(this);
    }

    if (args.length == 3) {
      right = args[1];
      options = args[2];
      if (left == right) return options.fn(this);
      return options.inverse(this);
    }

    if (eR.call(operator, left, right)) {
      return options.fn(this);
    }
    return options.inverse(this);
  };

  handlebars.registerHelper('is', isHelper);

  return eR;
};